WASHINGTON — Just two days after touting NASA's 2020 budget proposal at the Kennedy Space Center, the space agency's administrator admits a key test could be delayed further.

Jim Bridenstine testified before a Congressional Senate Committee Wednesday, saying further delays in the Exploration Mission-1 demo flight may prevent a June 2020 launch.

The flight involves an un-crewed Orion capsule and European Service Module flying on a 25 day, 1.3 million mile journey around the moon.

But right now, Bridenstine says construction of the SLS heavy lift rocket, which would launch both spacecraft at once, is falling behind, meaning the 2020 test flight may not hit its target date.

Bridenstine says using commercial rockets to launch EM-1 might be the best solution.

“We can use off the shelf capabilities to accomplish this objective for EM-1, but not change the direction of the SLS and EM-2,” Bridenstine said.

The EM-2 would carry crew on a test flight.

The first Orion capsule flight test launched on a commercial Delta IV Heavy back in 2014, because NASA's heavy lift rocket was still in development.